"Where's the beef?" is a stock phrase, which is synonymous with "Where's the substance?"

It came to public attention in a 1980s television commercial for the Wendy's chain of hamburger restaurants, featuring the elderly actress Clara Peller. After receiving a competitor's burger, the small patty prompts the gruff Peller to angrily exclaim "Where's the beef?" The first commercial was aired on January 9, 1984. The humorous ad and Peller's memorable character soon gave the catch-phrase a life of its own, and was repeated ad nauseam in countless TV shows, films, magazines, and other media outlets.

The phrase is now often associated with the 1984 U.S. presidential election. During primaries in the spring of 1984, when the commercial was at its height of popularity, Democratic candidate and former Vice President Walter Mondale ridiculed the candidacy of his rival, Senator Gary Hart by using the phrase during a televised debate before the New York and Pennsylvania primaries. Hart had portrayed his candidacy as based on "new ideas". Mondale said that Hart's claim to have "new ideas" made him wonder "Where's the beef?". The line is credited with stopping the momentum of the Hart campaign, allowing Mondale to pick critical victories to seal the nomination.

In an episode of the animated series The Simpsons, the line allegedly appeared on the front page of a newspaper in August 1984, during the 1984 Summer Olympic Games. In reality, Mondale had used the line earlier that spring and received the nomination by August.